In XLH, the excessive production of a protein called fibroblast growth factor 23 (FGF23) acts on the kidneys and promotes excretion of phosphate in the urine. This causes low phosphate levels in people with the disease, which in turn leads to the main symptoms of XLH, including softened and distorted bones, enlarged joints, bone pain, growth retardation, abnormal mineralization of the teeth, and leg bowing.
To correct any severe bone defects, especially bowing of the legs and skull deformities caused by the premature fusion of the skull bones, surgery may be needed.
Types of surgeries to treat XLH
The aim of surgical treatment is to achieve well-aligned lower limbs of equal length and horizontal and mobile knee and ankle joints.
The various types of surgeries that may be required to treat XLH patients include:
- Corrective surgery or osteotomy — a surgical procedure in which the bone is cut to correct a problem — to fix bowed or bent legs
- Osteotomy to fix bone deformities in the lower limb that can induce severe knee instability, coupled with guided growth techniques to correct defects before skeletal growth stops
- Bone stapling to correct angular defects in the lower limb by allowing growth on one side of the growth plate to catch up with the growth on the other side
- Fracture repair and joint replacements, especially in adult XLH patients with highly progressed osteomalacia (bone softening) and osteoarthritis, the most common form of arthritis
- Surgical repair to fix cartilage damage arising from the burden of weight-bearing on misaligned joints
- Neurosurgery to fix craniosynostosis, in which the brain sutures close prematurely and create problems with skull growth and pressure within the brain
- Neurosurgery to repair Chiari malformations, in which brain tissue extends into the spinal canal, causing both headaches and vertigo
- Surgery to remove parathyroid glands in some XLH patients who show increased parathyroid hormone levels that affect bones and other organs
Guidelines for surgery
The current guidelines for surgery in XLH patients are as follows:
- Surgery is recommended only when other medical interventions have been ineffective for at least 12 months
- Surgeons performing the operations must be experts in metabolic bone diseases
- The age of the child is an important criterion for surgery. For the surgical correction of lower limb bone deformities through guided growth, the preferred age is at least two to three years before skeletal maturity, which is age 14 for girls and age 16 for boys. On the other hand, for osteotomy, the preferred age is after achieving skeletal maturity in order to avoid complications. Emergency surgery is performed whenever necessary to fix fractures
- Clinical and functional assessments, including radiography, must be made at regular intervals after surgery. The follow-up must be made at 12 months post-surgery or earlier, to determine whether the bone deformity has been fixed or has worsened and whether there are any other clinical issues.
Any of the these XLH surgeries can cause complications. Moreover, surgery may be required multiple times in order to fix an issue. Therefore, surgery needs to be carefully considered under the guidance of a multidisciplinary care team to ensure best outcomes.
Last updated: Jan. 7, 2020
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